


That'll Teach You

by yyvanyy



Category: Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Desk Sex, F/M, Oral Sex, Plot What Plot/Porn Without Plot, Post-Canon, Shameless Smut, Teacher/Student Roleplay, Vaginal Sex
Language: English
Status: Completed
Published: 2020-07-02
Updated: 2020-07-02
Packaged: 2021-03-04 19:54:35
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 4,813
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25032037
Author URL: https://archiveofourown.org/users/yyvanyy/pseuds/yyvanyy
Summary: Dimitri, determined to fulfill Byleth’s request, tosses away any lingering doubt he held on to. And as the night progresses, the king finds himself growing confident in his ability to please his wife, but he forgets that she isn't one to be outdone.
Relationships: Dimitri Alexandre Blaiddyd/My Unit | Byleth
Comments: 4
Kudos: 107





	That'll Teach You

At first, Dimitri felt apprehension- no, at very first he felt embarrassment.

The scene replayed in his mind as he sat behind his desk, his back stiff against the large chair. He had forgotten how they had gotten on the topic, but his beloved coaxed him to confess some of his more... salacious thoughts of her. The king felt his face heat up, remembering the look Byleth had given him as she closed the distance between them and asked for him to continue, to describe every little detail about his lewd imaginings.

And so he had. He wouldn’t keep such things from her, after all, they were married, now a few months into their new lives. And the royal couple haven't wasted any time enjoying the conjugal nature of their new relationship. Dimitri understood that there was no real reason to hide the full extent of his adolescent infatuation from Byleth- but it didn’t make voicing such things any easier. 

He told her that, in the middle of the night, he would dream up indecencies where she and him would indulge in their carnal desires in the Blue Lion classroom. Dimitri told her that he would imagine her asking to speak to him once everyone had left the classroom. He told her how he imagined her praising him and his work ethic, all the while palming at his hardening member as she revealed to him how she planned to reward her favorite student. And he told her how he would pleasure himself as the scene played out in his mind.

He remembered the look she gave him when he confessed such things, her eyes dark and full of want; how she delicately held his face and brought him down for his lips to meet hers, the heat of her body pressed against his. She looked up at him through her lashes and he saw the growing hunger in those beautiful green eyes- 

“Oh Professor,” Byleth’s sweet voice broke Dimitri from his thoughts.

Right. It’s because of that confession that his beloved had convinced him to play out such fantasies with her. Though it wasn’t exactly what DImitri had pictured… He always imagined her in the role of the teacher and him as her student, as it had been, and now the roles were reversed. 

But, if this is what his beloved wife wanted from him, then he would fulfill whatever role she wanted him to play. Even if he was unsure of how to do it. 

And now they played in their bedchamber with Byleth in her old Garreg Mach Uniform and him in his old summer uniform. 

Dimitri sitting behind his large wooden desk, quickly regained his composure. Pushing away his thoughts, he focused on the present. And presently, Byleth was approaching him with a sheet of paper in her hand. 

And almost immediately, Dimitri’s eye began to wander. Her hair was down, falling over her shoulders and back, and she was wearing her pink headband along with her uniform just as she used to during her teaching days. But unlike those days, the top three buttons of her jacket were unbuttoned, cleavage exposed, breasts almost threatening to spill out. His eye continued moving down her bare legs, paying close attention to her thighs and the curve of her calves- stopping at the simple black, heeled shoes she wore then making his way back up to her face.

And as he noticed the playful smirk adorned on Byleth’s lips, he realized he was not very subtle in his staring. 

_“That damnable uniform will be the death of me…”_

Byleth continued speaking, “Professor Dimitri,” she placed a hand on the surface of the desk and leaned her weight down on her arm. She exaggerated the movements as she leaned forward, making sure to bring attention to her breasts, though she knew she didn’t need to. She enjoyed how attentive her husband was, and how shy he looked as he tried to keep eye contact and failed. “I’ve finished my assignment.” She handed him the paper.

As Dimitri began reading it, Byleth found it increasingly difficult to hold back her smile. Only the light of the fireplace and a few candles illuminated the darkness of the room, but it was enough to see the shining blue of his eye as it widened and his cheeks became flushed. 

The king had certainly been shy playing his role so he did not anticipate his beloved enjoying hers so much. And as he read on, it became more and more apparent how the contents of this paper betrayed her past as a mercenary. He had not expected his wife to be so... descriptive. 

He was confident that she could make even Sylvain blush- though he would not allow for the opportunity. 

Dimitri felt his ears growing hotter and he had to clear his throat as he tried to recover his composure. He placed the “assignment” down on, leaned back on his chair and crossed one leg over the other, “Miss Byleth, I’m afraid your work is lacking.” He was surprised at how steady his voice sounded. 

“Oh?” Byleth grabbed one of her husband’s pens on top of his desk. “Is that so, _Professor_?” She drew out the syllables, emphasizing the last word. “I think I did a good job, don’t you?” She brought the pen up to her face and began to outline the bottom of her lip with it. 

Before Dimitri could continue, Byleth deliberately threw the pen over her shoulder, “ _Oops!_ ” She kept her eyes on him as her coy smile widened. The thud of the pencil bouncing on the floor was deafening. “My, how clumsy of me…” She turned her back to him and walked to where the pen had landed behind her. And she slowly bent down, keeping her knees unbent and her rear in the air. Byleth shivered slightly as the chill of Fhirdiad crept up her skirt and over her skin.

Dimitri felt his heart miss a beat as he saw that his beloved had worn nothing under her skirt. He swallowed as his eye followed down her newly exposed skin, marveling at how lovely the soft lighting reflected off of her. She continued to linger in that pose even though the pen was back in her hand. 

She straightened herself and returned to him, seemingly unaware of how she had unrattled him, and placing the pen back in the wooden holder.

Byleth would be returning to Garreg Mach soon, and if this is what she wanted, if this is how she wanted to explore their intimacy-... The king’s hesitation had been silenced then. As Dimitri sat in his chair, he no longer cared about possibly making a fool of himself in front of his wife. No, now all that remained was a man starved, lusting for the touch of his wife. 

“Byleth,” Dimitri uncrossed his legs and pushed back his seat, leaving room in between his knees and the desk. “I’m disappointed. I expected more from my star student than that.” He pointed his chin towards the scandalous paper.

Byleth began to fidget with the hem of her skirt, lowering her eyes, “I’m sorry, Professor. Is there some way I can make up for it?” She felt her face start to heat up under the stern gaze of her husband as he feigned disappointment in her. “I’ll do _anything_...”

Dimitri didn’t hesitate, “Come here.” 

Byleth did as she was told and rounded the desk, approaching him until she was standing at his side. Dimitri reached for her hand and pulled her in front of him, guiding her to straddle his lap. Byleth made herself comfortable and leaned in close to his body, placing her hands to rest atop his shoulders. 

Dimitri became more encouraged as he felt her breasts press up against his body, “You’re going to have to complete an extra credit assignment if you wish to pass my class, Miss Byleth.” Byleth squirmed in his embrace as his hands pressed her body closer to him and began travelling down her back, caressing her bottom as they continued down and under her skirt. 

“Professor, we can’t do this!” Byleth protested, despite the fact that her thighs tightened their hold on Dimitri. “What if someone finds out?” Her hands felt down his chest.

Dimitri gave her ass a firm squeeze, “Then we’ll just have to not get caught.” It was his turn to smirk this time, and it was Byleth’s turn to blush as she stared into her husband’s piercing blue eye. She wasn’t sure if it was Fhirdiad that made her shiver, or him. A lump formed in her throat, and she felt the faint kindle of heat between her legs. 

All she could do was nod in response. 

Dimitri stretched up as Byleth lowered herself to him. He placed delicate kisses on her jaw then captured her lips. They kissed several times, at first chaste, but then they deepened as Byleth parted her lips so her husband’s tongue could explore her mouth. Their tongues danced against each other until Byleth separated to breathe.

Her husband took the opportunity and trailed kissed down to her neck and Byleth hummed, encouraging her husband to continue. And as Dimitri kissed, licked, and sucked leaving a few reddening marks here and there, his hands began to unbutton Byleth’s jacket. 

He was glad she wasn’t wearing her smallclothes as he quickly exposed her large breasts. He brought his hands up her back and to her shoulders, pulling her jacket down, it caught at her elbows. His hands soon came forward, caressing her sides and tits. He captured Byleth’s lips again, and he couldn’t help the small swell of pride when Byleth moaned into his mouth as he rubbed and pinched at her nipples.

He soon brought his mouth to her soft skin, licking and sucking at a hardening peak while a hand teased her other breast. Byleth let out a slow moan as she arched her back, letting Dimitri fondle and caress as he pleased. He switched to her other breast, not wanting to neglect any inch of her.

Byleth tugged at his hair and Dimitri let out a small growl in satisfaction. Her grip tightened as his teeth delicately pulled on her nipple. She let out a loud, sudden moan, but quickly brought her hands to cover her mouth in an attempt to stifle her voice. 

Dimitri reached for her hands and pulled them from her face, “Don’t hide your voice from me.” He switched to the other nipple, and Byleth began grinding her hips in his lap, trying to increase the yearning ache she felt between her legs. 

Dimitri leaned back as he watched Byleth writhe against him. He enjoyed how the marks he left behind looked as she tilted her head and arched her back, affording him a better view of his handiwork. 

He stifled a grunt as her hips continued to push against his growing erection. Dimitri’s hands continued to roam her body, almost frantically, as if he could not get enough of her. He continued to squeeze her breasts, mesmerize at their softness and how his large hands could not contain them. 

Byleth kissed Dimitri as her fingers began fumbling with his shirt. She managed to get his vest off and throw it on the floor, but grew impatient as she felt his cock hardening beneath her. She only managed to undo a few buttons on his shirt before giving up and moving her hand to his crotch, massaging his erection through his khaki pants.

Suddenly, Dimitri broke the kiss, grabbing Byleth’s hand and pulling it away from his bulge. Byleth, panting as she tried to catch her breath, could not hide the confusion in her eyes.

“There’s still much for you to learn, _Miss Byleth_.” Dimitri wrapped an arm around her waist while his other hand supported her bottom. “You’ll be staying after class.”

As Dimitri carefully placed her down to sit atop of his desk, Byleth brought one of her hands to her husband’s head and tangled her fingers in his hair, ensuring that she could pull him deeper into a kiss. Her lips felt sore from the intensity, but the feeling only encouraged her to keep tasting Dimitri more and more. 

His fingers brushed her shoulders and made their way over her nipples and down her stomach, stopping just at the waist of her skirt and his kisses trailed down her body again. Once he reached her stomach he lifted himself up to look at the mess his beloved had become. Her lips were red and swollen, she was panting roughly, her cheeks flushed and pink from their passion, her eyes dark with lust, and her skin glistening with sweat. 

Before he lost himself in her gaze, Dimitri continued his path of kisses. He kissed even lower down her abdomen, and his hands trailed her thighs that still held onto him and went beneath her skirt. He slowly lifted the hem up, pulling the garment to rest over her stomach as his head lowered to hover over her sex.

Byleth tried to close her legs, embarrassed with Dimitri being so close to her most intimate region, but his strong hands held her legs apart and prevented her from hiding. 

“... Dimitri?” Her voice was barely above a whisper, the anticipation in her voice palpable.

He smiled wolfishly as he saw the shine of her excitement peeking from her folds. He bagan leaving kisses on her inner thigh, slowly teasing his approach. Noticing the shiver that ran through her, he finally corrected her, “It’s _Professor_ Dimitri.” 

Byleth, now propped on her elbows, nodded as she watched him kiss closer and closer to her slit. Frustratingly, he backed away, and delicately began removing her shoes and socks. He laughed as he threw her footwear over the desk and she could only guess the look she gave him. She didn’t know how much longer she could handle his teasing as he slowly made his way back. She waited until he finally, slowly, gently licked the slit up to her hidden jewel. Byleth leaned her head back, moaning at the sensation.

Dimitri, a self satisfied smirk on his hips, continued toying with her. Byleth couldn’t help as her hips began to buckle at the sensation, trying to get him deeper into her. But Dimitri held her hips down as he gave more licks to her entrance. 

He straightened himself back up, licking her essence from his lips, and saw how quickly his wife’s chest lowered and rose as her breathing became more labored. But not yet, Dimitri couldn’t have her undone just yet. He wanted to pleasure her more until she begged for her release. 

Keeping his left hand at her hip, he brought his right thumb over her clit, ghosting the bundle of nerves. “Would you like to continue the lesson?”

Byleth’s face was hot. She laid back down on the desk and ran a hand through her sweat tousled hair, grabbing her headband and tossing it aside to the floor. She tried to buckle her hips again, she needed Dimitri’s thumb- she needed him to press harder. But his grip was too strong and he wouldn’t budge. She was certain he would leave bruises, but she didn’t care. She wanted to wake up in the morning and admire the marks his fingers left behind. She wanted to show them off to Dimitri and see the shame on his face and he realized he once again lost himself in their passionate lovemaking. 

“ _Please…_ ” Her voice, another whisper. She lifted herself up on her elbows again and faced him. Dimitri’s eye had gone dark, his pupil dilated with anticipation. “Professor- please _touch me_.” 

He didn’t know how long he would last with how she stared at him, with how she begged, but Dimitri was determined to bring her crashing down first. He finally brought his thumb down and began circling her clit, her arousal making his finger slick. He wanted to take his time and bring her slowly to the edge, only to then rip her away from it as she approached and do it all over again. 

That’s what he wanted, but as she desperately tried to move her hips and moaned his name over and over, his patience was losing out. Perhaps another time he would have the strength he needed, because tonight he didn’t think he did.

Dimitri let go of her hip and lifted her leg over his shoulder, exposing her sex further. He brought his mouth back to her bud and used his now free right hand to push his index finger inside her and her hand was at his hair again, her voice growing more desperate. He moved in and out of her as he whirled her clit with his tongue, adding a second and third finger as she cried out for more. 

Byleth began grinding her hips into his mouth as she felt the tension inside of her tense. “Dimitri-!” Her voice was wild and she tried to pull his head away, knowing her orgasm was soon approaching, but he refused to move. Her hips stuttered and the coiling in her stomach felt taught. When it finally snapped, she came arching her back and mouth open, a silent scream leaving her throat. The heat pooled in her stomach washed over her body as her cunt spasmed around Dimitri’s fingers. 

Her husband, having enjoyed the feeling of her nails digging into his scalp, removed his fingers from her core and brought them to his mouth, licking them clean. Dimitri removed himself from in between her legs as her body relaxed and kissed her stomach. His nails tenderly raked up her calves and her thighs, leaving goosebumps in their wake as his lips made their way to hers.

Byleth let out a soft laugh. She pushed at Dimitri’s shoulders and sat up on the desk. Her hand moved down his chest and stomach, stopping to rub at Dimitri’s dick, still in his pants. 

“Don’t tell me the lesson is over, Professor.” She unbuttoned his trousers, but stopped there. She got off the desk and pushed Dimitri further away from her. Reluctantly, he sat back down in his seat, his erection tugging at his pants uncomfortably and his eye never leaving hers. 

Byleth stood in front of Dimitri now and began removing the jacket that had been around her elbows. It pooled at the ground behind her as she lowered her arms, hands slowly trailing down her stomach, going further and further down, caressing either side of her pelvis and smoothing down the fabric of the skirt she still wore. She smiled as her husband’s sight trailed her fingers.

She moved up to Dimitri and bent her body down, bringing her hands to his face. She brushed his cheeks with her thumbs before her fingers moved to the back of his head. She closed her eyes and brought her lips delicately to meet his and removed his eyepatch. She was surprised it hadn’t come off yet with how much she had been pulling his hair. 

Dimitri tried to deepen the kiss, but she pushed him away. Her hand was at his face again as she caressed the bottom of his right eye, delicately touching the scar there. 

Dimitri stared at his wife. Before, he had been self-conscious to remove his eyepatch in front of her. He had been lucky that he did not lose his right eye and all that was left was a scar and useless, pale, blue iris. He didn’t know why he had been uncomfortable letting her see his eye uncovered. He told himself it was because he wanted to save her from it’s ugliness. But maybe it was deeper than that... maybe he didn’t want her to see it because it was a reminder of the time he had been without her. A reminder of all he had done to stay alive. 

But it didn’t matter anymore. It stopped being a concern some time ago. She was in his life now, and all he cared about was his desperate need for her love and her touch.

“You’ve taught me so well, Professor,” Byleth draped the eyepatch over the rounded carving atop Dimitri’s chair. Her hands began to undo the buttons on his shirt, “so let me show you what I’ve learned.” She opened his shirt and her hands were on the muscled skin of his chest and abs. Reaching his thighs, she spread his legs apart and lowered herself onto her knees in between them.

“Byleth…” Dimitri’s face grew hotter as he saw his wife on her knees before him. It seemed too vulgar to have a servant of Sothis in such a position. He briefly wondered if the Goddess would strike down as the stirring in his loins intensified. 

He let out a strangled moan as Byleth fumbled with his drawers and released his stiff member from the confines of his pants. Having ignored his own pleasure all night, even the slightest touch of her hands was overwhelming. Dimitri almost threw his head back, but he refused to look away from his beloved. 

She looked up at him, his cock in her hands, and his heart almost stopped. The confident smile tugging at her lips as she stroked him was almost too much to bear. Byleth stuck her tongue out and licked at the underside of his shaft. She continued leading a wet trail from the base to the tip to the head. Dimitri groaned, a trickle of precum dripping down his cock. 

“Does that feel good, Professor?” Goddess, his wife was going to drive him mad. She licked again, even slower this time. “Should we start the lesson?” Dimitri shut his eyes tight and exhaled deeply. He saw her smile even as his eyes could not, and that drove him even more wild. 

Dimitri opened his eyes to stare at her, he brought his hand to her head, and carefully moved her hair out of her face. His other hand was gripping at the armrest, threatening to split the wood. His breathing was heavier, more labored, as her tongue continued. 

Whatever words he wanted to say stuck in his throat as he tried to push them out, but he managed somehow, “ _Y- yes!_ ” That’s all he needed to say, all he needed to make clear that he _needed_ her to continue.

The king breathed in sharply, gasping for breath, as the queen’s mouth enveloped him. Byleth bobbed her head up and down taking as much of his cock into her mouth as possible. She couldn’t quite take all of him in, but it drove Dimitri just as wild. 

His hand at her head tightened involuntarily and he didn’t notice he had begun pushing down until he heard Byleth gag. 

Immediately, Dimitri released his hold on her, “I- Beloved, I’m so sorry!”

Byleth let him slide out of her mouth, and continued pumping at his dick with her hand. She tightened her grip on him and Dimitri let out another moan. She teased him, “So naugthy, Professor. I wonder how many times you’ve imagined me on my knees before you.” She brought her mouth to him and licked his balls.

All the while Dimitri struggled internally. He didn’t know what he should be more ashamed of: potentially hurting his wife, or how much he lusted for her even after causing her discomfort. Whichever it was, he figured he was right to recognize that shame was involved.

Byleth grabbed his hand and placed it back on her head, her mouth around his cock once more. 

Dimitri was determined not to lose himself in the throes of pleasure and tried to focus on keeping his composure. But that was easier said than done, as all he could focus on was the way Byleth’s tongue circled the tip of his head, on the noises she made, on the way her fingers fondled his balls, and how she looked with a mixture of her saliva and his precum dripping down to her chin. Dimitri continued to caress her hair, sometimes pushing the base of her head to have her take more of him in. Before he could apologize for his lack of self-control, his wife’s moans urged him on. 

He let his head fall back against the seat, a drawn out groan escaping him. He didn’t know how much longer he would last, but Dimitri kept pushing the heat pooling in his stomach away. He wanted to last longer, but the feeling persisted and kept trying to make its way to his crotch. Dimitri imagined that if it went on much longer, he would spill into his beloved’s mouth--

That was it. It was all Dimitri could handle and tugged at Byleth; his cock left her mouth with a plop. 

She stared up at him wondering if something was wrong. She admitted that she might have lost herself in the act, but she could have sworn Dimitri was enjoying it- 

She couldn't dwell on it longer, however, as he interrupted her thoughts, “I won’t last much longer,” Dimitri rose from the chair and helped Byleth to her feet, only to push her to lay back down on the desk. “Beloved, I must take you now.” 

Dimitri ripped the skirt she was still wearing off and Byleth spread her legs, inviting him in. Aligning himself with her entrance, he looked up at his wife once more. As she nodded, he slowly pushed himself in, finding immediate relief as her cunt clamped around his cock. 

Byleth shut her eyes, a moan escaping her lips as Dimitri filled her and took her as far as he could. Her inner walls constricted around him, swallowing him up and holding him tightly. Dimitri waited for Byleth to adjust, and began thrusting when Byleth began moving her hips. Dimitri stared at her large breasts bouncing with each thrust he made. The rhythmic noise of their bodies slapping against each other, the sound of their panting and moaning echoing throughout the room. 

Dimitri had both palms on the desk beside her shoulders, leaning over her as her hands held onto his wrists and she cried out his name. Her legs hooked tightly around his waist, welcoming him to go deeper and deeper in. 

He leaned down and kissed her, swallowing her mewling rapture. She was so tight, so warm, and her voice so alluring. Dimitri marvelled at how lucky he was that she loved him back, how lucky he was that she accepted the man he was before and the man he is now. 

His thoughts were brought back to the present as she called out to him, “I’m…” Byleth struggled to form words as the dense feeling in her abdomen returned, that familiar feeling of an orgasm rearing its head again, “I’m going to-” Another moan. She was close. 

Dimitri’s thrusts began to lose rhythm. “Beloved-!” His movements became erratic as his base instincts overwhelmed him and he looked for that final push he needed to release. Snaking a hand between their bodies, his thumb massaged her clit. He wanted her to cum first. 

Byleth’s toes curled and her breath hitched. “ _Fuck!_ ” She couldn’t handle the tension in her body any longer as he continued spearing her.

Reaching climax first, she shouted his name as her cunt convulsed around his cock, squeezing him and enticing him to also meet his end. He thrusted once, twice, and once more and released his seed into her. His hips jutted deep within her as his cock spurted and emptied itself inside her. Panting, he brought his head to rest at the crook of her neck, his member still throbbing. 

Wrapping her arms around him, caressing his hair and shoulders, Byleth helped Dimitri relax through his orgasm, and his breathing eventually evened out.

Dimitri began kissing her neck and nipping at her ear lobe. Byleth giggled as his hair tickled her skin, “What rank do you think you’ll receive after this, Professor?”

Dimitri pushed himself up, “Beloved- please!” His cheeks were getting red again. He only sighed as Byleth continued her beautiful laughing. Even if it was at his expense, he wished to hear it for the rest of his life. “Ha, that’ll teach me.” He ran a hand through his hair as he straightened, “Perhaps I shouldn’t be so eager to reveal my lecherous thoughts to you, Beloved.” He pulled his softening member out of her, and she felt his seed spill out of her. 

Byleth rose to sit up, still on his desk and pulled him in, hugging his chest. Dimitri kissed the top of her head as she spoke, “Then I guess I’ll have to tell you some of mine next time.” 

She smiled, knowingly, as he suddenly stiffened in her embrace.

**Author's Note:**

> Thank you so much for taking the time to read!  
> I hope the smut is good… that’s literally all this is so I apologize if it’s not. (Ｔ▽Ｔ)
> 
> Feedback is greatly appreciated as I’m always looking to improve my writing.


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